The invention relates to a suspension method for a bicycle frame, a suspension device for implementing such, a bicycle frame provided with said suspension device, especially for a rear wheel fork of said frame, and a bicycle equipped with such a frame.
The bicycles of the prior art, and especially the mountain bikes, are commonly provided with front wheel and/or rear wheel suspension devices in order to absorb shocks and vibrations for damping the bike during a ride. These devices comprise generally at least one spring (two for the front fork), usually coupled with a hydraulic piston. The hydraulic piston works with the spring in such a way that the wheels can move vertically within a range of motion of about 5 to 15 centimeters when climbing on a rock or passing above a pothole. Such suspension devices are placed either on the front fork and/or between the central rigid frame and a rear fork that supports the rear wheel.
These suspension devices are however heavy and complex to manufacture because of the numerous pieces. Furthermore, they are not easily mountable or dismountable, e.g. to fix or replace them, because of the tight combination of the pieces. Moreover, their efficiency is not sufficient in hard or extreme conditions (e.g. very rough ground, sports competition or high jump) because of the low range of vertical motion of the bike wheels equipped with such a suspension device.
It is an object of the present invention to provide a solution to at least one of the aforementioned problems.
For that purpose, the object of the invention is to provide a bicycle frame with an elastically deformable damping suspension for stabilizing purposes, that is more practical than springs and pistons usually used.
The invention relates more specifically to a suspension method for stabilizing a bicycle frame in order to absorb shocks, wherein said method consists of elastically deforming said suspension by a torsional effect perpendicularly to the bicycle frame.
The invention also relates to a suspension device to stabilize a bicycle frame extending over a frame plane and fitted out to implement such a method, and comprising damping torsional means about at least one axis contained in a torsional plane perpendicular to the frame plane.
In a preferred embodiment, such axis is perpendicular to the frame plane.
The invention also relates to a bicycle frame comprising:
a tubular rigid structure which extends substantially over a frame plane,
at least one wheel fork made up two tubular arms symmetrically arranged in view of the frame plane and defining a medium longitudinal direction in the frame plane,
at least one suspension device linking the wheel fork to the tubular rigid structure to absorb shocks,
wherein said suspension device comprises a damping means which is torsionally deformable about an axis, said axis being at an angle substantially ranged between 30 and 90 degrees regarding said medium direction, and preferably at right angles.
Preferably, said bicycle frame further comprises different means for connecting said damping means to the rear fork on one hand, and to the tubular rigid structure on the other hand.
Advantageously, one suspension device comprises a first rigid plate fixedly secured to the fork facing a second rigid plate fixedly secured to the rigid structure, and said damping means is a damping pad fixedly secured between and to the first and second rigid plates.
According to a preferred embodiment of the present invention, each of the two tubular arms of the wheel fork is linked to the tubular rigid structure by a suspension device comprising:
an external rigid plate fixedly secured respectively to internal parts of the arms of the fork,
an internal rigid plate fixedly secured to opposite sides of a tube of the tubular rigid structure,
each internal rigid plate facing an external rigid plate and a damping pad being respectively fixedly secured and arranged between a pair of internal and external rigid plates.
Preferably, the two suspension devices of a wheel fork are coaxial with a common axis perpendicular to the frame plane.
Each damping pad is preferably made of rubber and is permanently bonded to the internal and external rigid plates by means of vulcanization. Therefore, the damping means forms an integral unity with the plates.
According to preferred embodiments, each internal rigid plate is provided with two anti-rotational studs for its securing to the tubular rigid structure, and each external plate is provided with two holes for its securing to a tube of the rear fork.
Preferably, each damping means has a circular shape.
The invention also relates to a bicycle provided especially with said frame, the rigid structure of which having a crank gear, and two wheel forks, a front and a rear one to fit respectively a front and a rear wheel. In preferred embodiments, the wheel fork suspended is the rear wheel fork and said suspension device is arranged just above the crank gear and coaxial with said crank gear.